I'm sorry to hear you're experiencing pain from your shoulder down to your leg, especially when it worsens before your period. This type of pain could be related to several possible causes, including hormonal changes associated with your menstrual cycle.

One potential explanation is that hormonal fluctuations before your period might be affecting nerves or muscles, possibly linked to conditions like premenstrual syndrome (PMS) or dysmenorrhea (painful menstruation). Sometimes, conditions such as endometriosis or pelvic inflammatory issues can cause referred pain that radiates along the side of the body. Another possibility is nerve irritation, such as sciatica, which can cause pain radiating from the lower back or hip down the leg and might be influenced by hormonal changes.

Given the complexity and the range of possible causes, it is important to consult a gynecologist or a pain specialist. They can perform a thorough evaluation, including physical examination and possibly imaging or other tests, to determine the exact cause and recommend appropriate treatment.

If the pain is severe, worsening, or accompanied by other symptoms like numbness, weakness, or fever, please seek medical attention promptly.To narrow down potential causes, we will need some more information.Please tell me your age and gender.